CN107070467B - Simulate RF predistorter and non-linear separator - Google Patents

Abstract

The present invention relates to analog RF predistorters and nonlinear splitters. An RF transmitter device using analog predistortion is disclosed. The device includes a lower bandwidth circuit, an analog predistorter and a non-linear amplifier chain. The lower bandwidth circuit is configured to generate an analog signal. The analog predistorter is configured to apply nonlinear distortion to the analog raw signal based on the coupled feedback signal to generate an RF output signal. The nonlinear amplifier chain is configured to amplify the RF output signal to generate a transmit signal relative to the analog original signal. A coupled feedback signal is derived from the transmission signal.

Description

Analog RF Predistorter and Nonlinear Splitter

Background technique

Communication systems typically use transmission signals centered around a carrier frequency of a defined channel. Information is communicated by representing the information using modulation based on amplitude, phase, frequency, and/or combinations thereof. Information is sent by one or more signals on a frequency band around the carrier frequency.

Radio frequency (RF) power amplifiers are commonly used for modulation, such as amplitude modulation. RF power amplifiers are required to operate over a wide range of frequencies and power levels.

Ideally, an RF power amplifier would be linear and have an output that is a linear value of the input. However, RF power amplifiers typically exhibit some type of nonlinearity in their behavior. This non-linearity results in a non-linear variation of the output signal compared to the input signal. Non-linear changes degrade communications and increase power consumption.

Description of drawings

FIG. 1 is a diagram illustrating an RF transmitter system incorporating an analog predistorter.

FIG. 2 is a diagram illustrating a lower bandwidth circuit.

FIG. 3 is a diagram illustrating a parameter generator.

FIG. 4 is a diagram illustrating an analog IQ processor.

FIG. 5 is a diagram illustrating a spline generator.

FIG. 6 is a graph illustrating the generation of RF signals by the analog IQ processor 104 .

7 is a graph illustrating the use of a spline generator and a parametric generator to generate a non-linear function for a square root function.

8 is a block diagram depicting a memory spline generator with multiple memory items.

9 is a block diagram illustrating an RF transmitter system incorporating an analog predistorter and having multiple delays.

10 is a diagram illustrating an RF transmitter system utilizing multiple analog IQ processors.

11 is a diagram illustrating an RF transmitter system utilizing multiple analog IQ processors and multiple bandwidth splitters.

Figure 12 is a flowchart illustrating a method of operating an analog predistorter.

Detailed ways

The present invention will now be described with reference to the various figures of the drawings, in which like reference numerals are used to refer to like elements throughout, and in which the illustrated structures and devices are not necessarily drawn to scale.

Systems, methods, devices and embodiments incorporating an analog RF predistorter for a power amplifier are provided. An analog predistorter boosts the output of the power amplifier by making the system more substantially linear and more linear than a system without a predistorter.

A predistortion system (also known as a predistorter) is a system that precedes a non-linear device such as a power amplifier in order to linearize the overall system. Linearization can increase electrical efficiency, maintain spectral purity, meet spectral requirements, maintain in-band signal quality, and more.

One technique to accomplish predistortion and facilitate linearization is to utilize a digital predistorter, which is a non-linear system block implemented in the digital baseband domain of a system such as a transmitter system. A digital predistorter modifies or predistorts an input or original signal such that a non-linear device produces a linear or substantially linear output. For example, a cascade of a digital predistorter and a non-linear power amplifier provides an output that is a linearly amplified version of the original or input signal.

One of the drawbacks of using a digital predistorter is that the digital predistorter further broadens or expands the frequency spectrum of its input signal. As a result, components or blocks of the system are required to handle much higher bandwidths, such as in one example approximately 5 times the bandwidth of the case without digital pre-distortion of the original signal. Higher bandwidth requires more expensive components, such as digital-to-analog converters, mixers, etc.; and results in higher power consumption.

Furthermore, the use of digital predistorters in smaller systems, such as smaller base stations, handheld devices, etc., can consume so much power that overall transmitter efficiency suffers from digital predistorter power consumption.

The systems and methods described below utilize analog predistorters that introduce predistortion, such as in the RF domain, closer to non-linear devices. As a result, the baseband components and analog RF front end avoid handling the widened or extended spectrum and consequent higher bandwidth signals. Thus, the components consume less power than components of a system incorporating a digital predistorter.

FIG. 1 is a diagram illustrating an RF transmitter system 100 incorporating an analog predistorter. System 100 uses lower bandwidth components than digital predistortion systems due to predistortion occurring in the analog domain and closer to non-linear devices. System 100 may be configured at least partially in circuitry and/or other hardware components. Additionally, system 100 may be an apparatus.

System 100 includes lower bandwidth circuit 102 , analog IQ processor, preamplifier 106 , RF power amplifier 108 , spline generator 110 , parameter generator 112 , and envelope detector 122 .

Lower bandwidth circuitry 102 typically includes a baseband processor, digital-to-analog converter, and IQ mixer. Circuit 102 operates at a lower bandwidth than other RF transmitters because IQ mixing is done before predistortion including digital predistortion.

The lower bandwidth circuit 102 is configured to generate a mixed signal having I (in-phase) and Q (90 degree shifted quadrature) components as an input signal 116 , also referred to as the original signal. The input signal 116 represents information with modulation based on amplitude, phase, frequency, and/or combinations thereof. The spectrum of the input signal 116 is the original spectrum that has not been expanded or broadened. Additional details of suitable lower bandwidth circuits are provided below.

Analog IQ processor 104 is configured to receive input signal 116 and process input signal 116 in the analog domain to generate RF output signal 124 . Analog IQ processor 104 divides input signal 116 into upper and lower quadrature signals within processor 104 . The upper signal is not phase shifted, while the lower signal is phase shifted by 90 degrees. Processor 104 is configured to predistort the upper and lower signals in both magnitude and phase by multiplying each with a non-linear function or functional. The predistorted up and down signals are then added to generate the RF output signal 124 including nonlinear predistortion. Nonlinear predistortion represents the nonlinear behavior of the power amplifier 108 .

Envelope detector 122 is configured to receive input signal 116 and to detect and provide an envelope 126 of signal 116 . The envelope detector 122 may be implemented, for example, using a rectifier followed by a low pass filter, however other suitable implementations are contemplated.

Parameter generator 112 is configured to generate predistortion parameters from envelope 126 and coupled signal 118 . Envelope 126 is provided by envelope detector 122 and is based on original signal 116 . Coupled signal 118 is a coupled version of RF output signal 128 generated by power amplifier 108 . A coupler or similar component (not shown) acquires the coupled signal 118 without substantially changing the RF output signal 128 .

The parameter generator 112 generates the predistortion parameters 114 using a suitable mechanism. Generally, a digital controller circuit (not shown) is used to generate the predistortion parameters 114 . In one example, a table or storage element within the digital controller circuit is used to provide parameters 114 based on entries from envelope 126 and/or coupled signal 118 . For example, an erasable programmable read-only memory (EPROM) can be used as the storage element or table. The tables and associated parameters 114 may be developed during the calibration and or fitting process.

In another example, a parameter estimation algorithm is used by a digital controller circuit to generate predistortion parameters 114 based on coupled signal 118 and envelope 126 . It is to be appreciated that the predistortion parameters 114 may be provided at relatively low speeds, such as less than 1 MHz.

The spline generator 110 is configured to provide one or more nonlinear functions/functionalities 120 , also referred to as splines, to the analog IQ processor 104 . Spline generator 110 generates function 120 from envelope 126 of original signal 116 and predistortion parameters 114 . The non-linear function 120 mimics or represents the non-linear behavior of or from the inverse section of the power amplifier 108 .

In one example, nonlinear function 120 includes an upper function and a lower function. The upper function can be used for the upper signal or the in-phase component, while the lower function is used for the lower signal or the quadrature component.

The pre-power amplifier 106 applies pre-amplification to the RF output signal 124 . Power amplifier 108 then amplifies RF signal 124 to generate RF transmit signal 128 . The power amplifier 108 typically introduces non-linearity into the RF transmission signal 128 . However, RF signal 124 has been predistorted in the analog domain. Analog predistortion results in a substantially linear transmission signal 128 with respect to output signal 128 without analog IQ processor 104 . Pre-power amplifier 106 and power amplifier 108 are also referred to as a power amplifier chain. It is to be appreciated that the chain may omit pre-amplifier 106 in some variations. Furthermore, it is to be appreciated that power amplifier 108 may include variations including, but not limited to, multiple inputs.

As a result, RF transmitter system 100 produces RF transmission signal 128 that is substantially linear with respect to output signal 128 without analog IQ processor 104 . Lower cost and/or complexity circuits may be used because circuit 102 operates at a lower bandwidth. The circuit 102 operates at a lower bandwidth because the spectrum of the original signal 116 is not expanded to account for digital predistortion, as is the case in other schemes.

FIG. 2 is a diagram illustrating the lower bandwidth circuit 102 . Circuit 102 is provided as an example of a suitable circuit. It will be appreciated that suitable variants are contemplated.

The lower bandwidth circuit 102 generates an analog signal, referred to as an input or raw signal 116 . The circuit 102 includes a baseband processor 202, a digital-to-analog converter (DAC) 204, a mixer 206 and a summing block 208 as well as other possibly required passive components, such as for example a low-pass filter, which are not explicitly shown in FIG. 2 out.

Baseband processor 202 generates up and down digital signals. The up signal is received by up DAC 204i and converted to an analog up signal. The analog up signal is received by upmixer 206i and mixed with the oscillating signal to generate an upmixed signal.

The down signal is received by the down DAC 204q and converted to an analog down signal. The analog down signal is received by down mixer 206q and mixed with the oscillating signal to generate a down mixed signal. The summation component 208 adds or sums the up- and down-mixed signals to generate the input signal 116 .

Baseband processor 202, digital-to-analog converter (DAC) 204, mixer 206, and summing component 208 may be implemented with low-cost circuitry. The up and down signals of circuit 102 are at the original bandwidth that has not been expanded or widened. as a result. Circuits may be composed of lower cost components/circuit elements. In contrast, baseband processors associated with digital predistortion can require spectral expansion or bandwidth increases of up to 5x or greater.

FIG. 3 is a diagram illustrating the parameter generator 112 . Parameter generator 112 generates predistortion parameters 114 used by spline generator 110 . The parameter generator 112 is provided as an example for purposes of illustration, and it is to be appreciated that suitable variations are contemplated.

The parameter generator 112 includes a first analog-to-digital converter (ADC) 302 , a digital controller 304 and a second ADC 306 . The first ADC 302 converts the envelope 126 from analog to digital. Mixer 308 mixes coupled signal 118 with a local oscillator signal (LO) to generate a coupled baseband equivalent power amplifier output signal. The second ADC 306 converts the hybrid coupled signal from analog to digital.

A digital controller 304 receives the digitally coupled baseband signal and digital envelope and generates predistortion parameters. The controller 304 is configured to generate the predistortion parameters 114 based on the digital envelope and the digital hybrid coupled signal.

The digital controller 304 may compare the pre-amplified signal, the digital envelope signal and the digital hybrid coupled signal. The digital controller 304 may use a look-up table or similar component to generate the predistortion parameters. Alternatively, the digital controller 304 may implement a parameter estimation algorithm based on the values of the digital envelope signal and the digital hybrid coupled signal.

FIG. 4 is a diagram illustrating the analog IQ processor 104 . Processor 104 is provided as an example, and it is to be appreciated that suitable variations are contemplated.

Analog IQ processor 104 receives an analog signal, an input signal 116 , and mixes the input signal with one or more nonlinear functions or splines 120 . The mixed signal is added and provided as RF signal 124 for amplification by pre-amplifier 106 and power amplifier 108 . RF signal 124 includes nonlinear predistortion based on a nonlinear function. The nonlinear predistortion estimates and/or represents the nonlinear behavior of the power amplifier 108 .

Analog IQ processor 104 includes a phase shifting component 404 , an upmixer 406i , a downmixer 406q and a summing component 408 . The phase shifting component 404 shifts the input signal by a number of degrees. In this example, the phase shifting component 404 is a Hibbert transformer (HT) and shifts the input signal by 90 degrees.

Upmixer 406i receives input signal 116 and mixes input signal 116 with up or in-phase nonlinear function 120i. The mixed in-phase signal is then received by summing component 408 . Similarly, down-mixer 406q receives the shifted input signal and mixes the shifted input signal with down or quadrature non-linear function 120q. The mixed quadrature signals are also received by summing component 408 . Summing component 408 combines the mixed quadrature signal and the mixed in-phase signal to generate RF signal 124 .

FIG. 5 is a diagram illustrating the spline generator 110 . Spline generator 110 is an example of a suitable spline generator that may be used with RF transmitter system 100 of FIG. 1 . It is to be appreciated that suitable variations of the spline generator 110 are contemplated.

Spline generator 110 receives envelope 126 of original signal 116 and generates one or more nonlinear functions 120 . The non-linear function 120 is also known as a spline. Non-linear function 120 is generated based on envelope 126 and predistortion parameters 114 from parameter generator 112 .

The spline generator 126 includes a summing component 502 , an absolute value component 504 , a mixer 506 and a summing component 508 . Summation components 502 each receive an envelope 126 and a different parameter. The output of summation component 502 is received by absolute value component 504, which generates an absolute value.

Mixer 506 combines the corresponding output of absolute value component 504 with additional parameters. The mixed output is provided to summation component 508 , which combines the output into nonlinear function 120 .

Discuss Figures 1-5 in combination. Raw modulated RF signal 116 generated by lower bandwidth circuit 102 is passed through To represent. Raw signal 116 is divided into two quadrature signals (an upper signal and a lower signal) within analog IQ processor 104 . The upper signal is not modified from the original signal 116 . The lower signal is phase shifted by 90° using the Hibbert transformer 404 shown in FIG. 4 to obtain the signal . As a result, the analog IQ processor 104 includes two quadrature signals that can be non-linearly predistorted in the magnitude and phase domains by multiplying the signals with the non-linear function 120 at multipliers 406i and 406q.

Nonlinear Functions 120 through and To represent. where f ₁ represents the first non-linear function 120i and f ₂ represents the second non-linear function 120q. The term τ _N represents the added time delay or storage. The mixed signals are summed by a summation component 408 to generate the predistorted RF signal 124 . The predistortion accounts for the non-linear behavior of the power amplifier 108 and facilitates generation of the RF transmission signal 128 with the required linearity and output power. Thus, the predistorted RF signal 124 is provided to the preamplifier 106 and then to the power amplifier 108 .

If the temporal correlation from the (low frequency) baseband signal is removed, the RF signal 124 can be represented by the equation shown below and described as a function of the amplitude a by

This equation shows that both the amplitude and the phase of the RF output signal are nonlinearly related to the signal amplitude a . The nonlinear function is described by a generalized storage spline generator 110 .

FIG. 6 is a graph 600 illustrating generation of RF signal 124 by analog IQ processor 104 . Graph 600 is provided for illustrative purposes and to facilitate understanding.

The x-axis plots the magnitude of the in-phase component/phase of the RF signal 124 and the y-axis plots the magnitude of the quadrature phase of the RF signal 124 . The angle or phase of RF signal 124 is shown by angle 601 . Line 602 depicts the amplitude of RF signal 124 .

Line 602 is obtained by the following formula:

Angle 601 is obtained by the following formula:

Storage spline generator 110 generates nonlinear function 120 . Referring to the spline generator 110 shown in FIG. 5, the first nonlinear function can be obtained by:

And the second nonlinear function can be obtained by:

where τ ₀ =0, K represents the number of segments, and β _k is defined to normalize the input signal amplitude segment boundaries, and M represents the memory depth. The stored spline generator 110 uses a programmable parameter vector to define the desired non-linear function. Programmable vectors are shown as:

,and .

Programmable vectors c , d and β (also referred to as predistortion parameters 114 ) are obtained from parameter generator 112 via a digital interface.

FIG. 7 is a graph 700 illustrating the use of the spline generator 110 and the parameter generator 112 to generate a non-linear function for a square root function.

Line 705 is represented by The square root function given by, where , with segments using K=2 (where segment boundaries ) of simple splines. Line 701 is made by given constant. Line 702 is made by Represents the linear part of the formula. The piecewise affine function is represented by line 703 and passes through A spline/non-linear approximation shown by line 704 combining 701 , 702 and 703 is given and derived.

Thus, line 704 represents a spline/non-linear approximation of the square root formula using two segments and no memory. A more accurate approximation can be obtained by increasing the number of segments.

It is to be appreciated that a power amplifier may have a non-linear memory effect as part of the non-linear behavior of the power amplifier. Storage terms are used to represent and account for these non-linear storage effects. storage items are shown above as .

8 is a block diagram depicting a stored spline generator with multiple stored items. A plurality of storage terms is used to generate a non-linear function 120 representing the effects of non-linear storage.

The spline generator of FIG. 8 includes a delay element ₈₀₂ , a plurality of memory spline generators 110 ₀ , 110 ₁ , . Each individual spline generator operates as shown in Figure 5.

Delay element 802 delays signal or envelope 124 by a delay amount from 1 to M. Thus, each spline generator 110 generates a varying spline/non-linear function based on its input. For example, spline generator 1100 generates splines based on _zero or no delay. The spline generator ₁₁₀₁ generates _a spline based on the delay T1. Continuing, spline generator _110M generates a spline delay based on delay _TM . A summation component 808 adds the output of the spline generator 110 to provide a collective non-linear function.

9 is a block diagram illustrating an RF transmitter system 900 incorporating an analog predistorter and having multiple delays. Multiple delays are used by multiple analog IQ processors to generate multiple RF signals. Multiple RF signals are combined to derive a single RF signal. Portions of system 900 such as lower bandwidth circuits and power amplifiers are omitted to facilitate understanding.

System 900 includes a plurality of delay elements 902 , a plurality of analog IQ processors 104 and a summation component 908 . The first IQ processor ₁₀₄₀ receives an input/raw signal 116 that has been generated by a lower bandwidth circuit. _{The second} IQ processor 1042 receives the input signal 116 delayed by the delay element T1. The nth IQ processor _{104N receives the input signal 116 delayed by the delay element TN .}

Analog IQ processor 104 receives nonlinear function 120 from a spline generator. In one example, the spline generator provides the same nonlinear function to all analog IQ processors 104 . In another example, a spline generator provides a different nonlinear function to each analog IQ processor 104 .

Multiple IQ processors 104 generate multiple RF output signals. These signals are combined or added by summing component 908 to generate RF output signal 124 .

FIG. 10 is a diagram illustrating an RF transmitter system 1000 utilizing multiple analog IQ processors. System 1000 operates multiple analog IQ processors in parallel to enhance linearity and efficiency.

System 1000 omits some elements to simplify the diagram and improve understanding.

System 1000 includes multiple analog IQ processors 104 , envelope detector 122 and spline generator 110 . The envelope detector 122 detects or acquires the envelope 126 of the input/raw signal 116 . Spline generator 110 uses the envelope along with predistortion parameters 114 to generate a plurality of nonlinear function pairs. Each pair includes an upper function and a lower function. The upper function is also called the in-phase nonlinear function and the lower function is also called the orthogonal nonlinear function. Thus, the spline generator 110 generates N+1 pairs of nonlinear functions.

Each IQ processor receives an associated pair of nonlinear functions and generates an RF output from the input signal 116 . The respective RF outputs are summed together and provided as a single RF output signal.

11 is a diagram illustrating an RF transmitter system 1100 utilizing multiple analog IQ processors and multiple bandwidth splitters.

System 1100 is similar to system 100 described above and the description of system 100 may be referenced for additional description.

System 1100 includes a plurality of analog IQ processors 1104 that generate a plurality of RF output signals. These signals are combined into a single RF output signal 124 .

System 1100 also includes a plurality of separators 1106 . Splitters segment the RF output signal into segments based on bandwidth or spectrum. Each splitter has an associated amplifier chain that generates the transmit signal. The associated amplifier chain has multiple amplifier chains 1108 and typically includes preamplifiers and power amplifiers.

Multiple amplifier chains 1108 generate multiple transmit signals that are combined into a single signal, such as by a power combiner.

FIG. 12 is a flowchart illustrating a method 1200 of operating an analog predistorter. Method 1200 applies nonlinear predistortion in the analog domain rather than the digital domain. As a result, the frequency spectrum of the signal is maintained to the original width and the required bandwidth of the signal is reduced. Nonlinear predistortion accounts for the nonlinear behavior of power amplifiers or other components.

The method begins at block 1202 where a baseband processor of a lower bandwidth circuit generates a digital baseband signal. The digital baseband signal includes information content.

At block 1204, the digital-to-analog converters and mixers of the lower bandwidth circuitry convert and mix the digital baseband signals to generate analog raw signals. The analog original signal is at the original spectral width because the analog original signal is not widened as in digital predistortion. Simulate the original signal including the modulation scheme.

At block 1206, the analog IQ processor applies predistortion to the analog raw signal to generate an RF signal. Predistortion is based on one or more nonlinear functions. In one example, the IQ processor includes a phase shifting component that separates the quadrature components from the original signal. The original signal is mixed with a first nonlinear function to generate a mixed in-phase signal, and the quadrature component is mixed with a second nonlinear function to generate a mixed quadrature signal. The mixed in-phase signal and the mixed quadrature signal are combined to provide an RF signal.

At block 1208, the spline generator generates one or more nonlinear functions based on the envelope and predistortion parameters of the original signal. In one example, the spline generator generates a first nonlinear function for the upper signal or in-phase component and a second nonlinear function for the lower signal or quadrature component. An envelope detector can be used to detect or generate the envelope of the original signal.

At block 1210, the nonlinear power amplifier amplifies the RF signal to generate a transmit signal. A power amplifier has nonlinear behavior, which has been estimated by one or more nonlinear functions. As a result, the transmission signal is generated substantially linearly compared to if no linearization would be applied. At block 1212, a parameter generator generates predistortion parameters based on the coupled feedback signal and the envelope of the original signal. Parameter generators typically include digital controls that provide parameters. In one example, the predistortion parameters are in the form of programmable vectors.

While methods are illustrated and described below as a series of acts or events, it will be appreciated that the illustrated order of such acts or events is not to be construed in a limiting sense. For example, some acts may occur in a different order and/or concurrently with other acts or events than those illustrated and/or described herein. In addition, not all illustrated acts may be required to implement one or more aspects or embodiments of the disclosure herein. Furthermore, one or more actions depicted herein may be performed in one or more separate actions and/or stages.

It is to be appreciated that the claimed subject matter can be implemented as a method, apparatus, or article of manufacture using standard programming and/or processing techniques to produce software, firmware, hardware, or any combination thereof to control a computer to implement the disclosed subject matter (e.g., The systems, devices, etc. shown in Figures 1, 2, etc. are non-limiting examples that can be used to implement the above methods). The term "article of manufacture" as used herein is intended to cover a computer program accessible from any computer-readable device, carrier, or media. Of course, those skilled in the art will recognize many modifications may be made to this configuration without departing from the scope or spirit of the claimed subject matter.

An RF transmitter device using analog predistortion is disclosed. The device includes a lower bandwidth circuit, an analog predistorter and a non-linear amplifier chain. The lower bandwidth circuit is configured to generate an analog signal. The analog predistorter is configured to apply nonlinear distortion to the analog raw signal based on the coupled feedback signal to generate an RF output signal. The nonlinear amplifier chain is configured to amplify the RF output signal to generate a transmit signal relative to the analog original signal. A coupled feedback signal is derived from the transmission signal.

Another RF transmitter device is disclosed. The device includes an analog IQ processor, an envelope detector, a spline generator, a parameter generator and a nonlinear power amplifier. The analog IQ processor is configured to generate an RF signal from the analog raw signal based on a non-linear function. The envelope detector is configured to obtain the envelope of the simulated raw signal. The spline generator is configured to generate a non-linear function based on the envelope and predistortion parameters. The parameter generator is configured to generate predistortion parameters based on the envelope and the coupled feedback signal. The nonlinear power amplifier is configured to generate a transmission signal from the RF signal.

A method of operating an analog predistorter is disclosed. The digital baseband signal is converted and mixed to generate an analog raw signal without increasing the spectral width. Nonlinear predistortion is applied in the analog domain to the analog raw signal according to one or more nonlinear functions to generate a distorted RF signal. Generates a nonlinear function based on the envelope and predistortion parameters that simulate the original signal. The distorted RF signal is amplified with a nonlinear amplifier to generate a transmit signal.

With particular reference to the various functions performed by the above-described components or structures (components, devices, circuits, systems, etc.), terms (including references to “members”) used to describe such components are intended to correspond to (unless otherwise indicated) ) any component or structure that performs the specified function of the described component (eg, it is functionally equivalent), even if the disclosure is not structurally equivalent to performing the function in the exemplary implementations of the invention described herein Structure. Furthermore, while particular features of the invention may have been disclosed with respect to only one of several implementations, such features may be combined with one of the other implementations as may be desired and advantageous for any given or particular application. or a combination of other features. Additionally, to the extent that the terms "comprises", "comprises", "has", "has", "with" or variations thereof are used in any of the detailed description and claims, such terms are intended to be used similarly to the term "comprising " way is inclusive.

Claims (18)

1. An RF transmitter apparatus using analog predistortion, said apparatus comprising: an analog IQ processor configured to apply a nonlinear distortion to the analog raw signal based on one or more nonlinear splines to generate an RF output signal; a spline generator configured to generate one or more nonlinear splines based on the envelope of the simulated original signal and one or more predistortion parameters; a parameter generator configured to generate one or more predistortion parameters based on the envelope and the coupled feedback signal; and A nonlinear amplifier chain configured to amplify the RF output signal to generate a transmit signal relative to the analog original signal, wherein a coupled feedback signal is derived from the transmit signal. 2. The apparatus of claim 1 , further comprising a lower bandwidth circuit configured to generate an analog raw signal, wherein the lower bandwidth circuit includes a baseband circuit configured to generate the first digital signal and the second digital signal a processor, and a first digital-to-analog converter configured to convert the first digital signal to a first analog signal, and a second digital-to-analog converter configured to convert the second digital signal to a second analog signal. 3. The apparatus according to claim 1 , further comprising a lower width circuit configured to generate an analog raw signal, wherein the lower bandwidth circuit comprises: a mixer for combining the first analog signal with the oscillator signal mixing to generate a first mixed signal; and a summation component configured to add the first mixed signal and the second mixed signal to generate an analog original signal, wherein the first mixed signal is at the original bandwidth. 4. The apparatus of claim 1, wherein the nonlinear amplifier chain comprises a power amplifier exhibiting nonlinear behavior. 5. The apparatus of claim 1, wherein the non-linear amplifier chain comprises a preamplifier and a power amplifier connected in series. 6. The apparatus of claim 1 , wherein the analog IQ processor is configured to apply a first nonlinear function to the in-phase component of the analog raw signal and apply a second nonlinear function to the quadrature component of the analog signal, wherein the first and The second nonlinear function represents the nonlinear behavior of the nonlinear amplifier chain. 7. The apparatus of claim 6, wherein the analog IQ processor includes a phase shifting component configured to generate quadrature components of the analog raw signal. 8. The apparatus of claim 1, wherein the spline generator uses segments and memory to estimate the nonlinear behavior of the nonlinear amplifier chain. 9. The apparatus of claim 1, wherein the parameter generator comprises a digital controller configured to generate parameters from a memory based on the coupled feedback signal and an envelope of the simulated raw signal. 10. An RF transmitter apparatus using analog predistortion, the apparatus comprising: an analog IQ processor configured to generate an RF signal from the analog raw signal based on one or more nonlinear splines; an envelope detector configured to obtain the envelope of the simulated raw signal; a spline generator configured to generate a non-linear spline based on the envelope and predistortion parameters; a parameter generator configured to generate predistortion parameters based on the envelope and the coupled feedback signal; and A nonlinear power amplifier configured to generate a transmission signal from an RF signal. 11. The apparatus of claim 10, further comprising a lower bandwidth circuit configured to generate a baseband signal and convert the baseband signal to an analog raw signal. 12. The apparatus of claim 10, further comprising a splitter configured to segment the RF signal into a plurality of signal segments, and wherein the power amplifier has a plurality of inputs configured to receive the plurality of signal segments. 13. The apparatus of claim 10, wherein the analog IQ processors comprise a plurality of IQ processors configured to process delayed versions of the analog raw signals. 14. The apparatus of claim 13, wherein a plurality of IQ processors generate a plurality of RF signals that are provided to a plurality of inputs of a power amplifier. 15. The apparatus of claim 10, wherein the spline generator is configured to use a number of segments and a memory depth that provide suitable linearization. 16. A method of operating an analog predistorter, the method comprising: Convert and mix digital baseband signals to generate analog raw signals without adding spectrum; applying nonlinear predistortion in the analog domain to the analog raw signal according to one or more nonlinear functions to generate a distorted RF signal; generating one or more predistortion parameters based on simulating the envelope of the original signal and the coupled feedback signal; generating one or more non-linear functions based on the envelope of the simulated original signal and the one or more predistortion parameters; and The distorted RF signal is amplified with a nonlinear amplifier to generate a transmission signal. 17. The method of claim 16, wherein applying nonlinear predistortion includes separating the analog raw signal into in-phase and quadrature components, and mixing the in-phase component with a first nonlinear function and mixing the quadrature component with a second non-linear function linear function. 18. The method of claim 16, further comprising generating one or more predistortion parameters based on a coupled feedback signal of the transmission signal.